The present invention relates to an improved process for the manufacture of 1,3,5-trioxane, also known as sym-trioxane, and which is referred to in the present specification and claims as "trioxane".
The manufacture of trioxane by distilling aqueous formaldehyde solutions in the presence of an acid catalyst is old and well known in the art. It is also known to accomplish the distillation of the aqueous formaldehyde solution while the latter is intimately mixed with an immiscible, non-volatile, oily liquid phase. For example the use of an oily phase consisting of a diester of o-phthalic acid is disclosed in U.S. Pat. No. 3,637,751 issued Jan. 25, 1972, to Fuchs, et al. U.S. Pat. No. 3,310,572 issued Mar. 21, 1967, to Delle, et al., discloses the use of liquid paraffin as well as synthetic lubricating oils, such as polypropylene glycols, as the oily phase. It is to such a type of process wherein the oily phase is substantially non-volatile and substantially inert under the conditions of the distillation that the present invention is directed.
Although various compounds have been disclosed in the literature as the oily phase in a process of the foregoing type, each has some disadvantages. Despite the drawbacks of some of the particular oily phases described in the prior art, many advantages are to be gained by their use, and thus the discovery of new and improved compounds for use as the oily phase is desired.
It is thus an object of the present invention to provide a new and useful process for the manufacture of trioxane. It is a particular object to provide an improvement in the processes as described above wherein trioxane is produced by distillation of an aqueous formaldehyde solution while it is intimately mixed with a non-volatile, immiscible, oil liquid phase. Additional objects will become apparent from the following description of the present invention.